1. Field of the Invention
The invention relates to the field of termination of tension members for elevators. More particularly, the invention relates to improved method and apparatus for terminating a flexible flat tension member having a plurality of load bearing cords therein for an elevator car lifting assembly.
2. Prior Art
Flexible tension members whether they be flat, round, or other shaped, require termination in order to be useful. Many different types of terminations have been used for each of the distinct types of tension members that have been employed in arts where tension members are needed. Eyes have been woven into round cross-section tension members or created by other materials through which the tension member will pass; ferrules have often been employed to create eyes in tension members; u-bolts and other compression members including plates have also been employed to create eyes in tension members; and adhesive type materials have been used to pot tension members in termination fixtures. Particularly with respect to the elevator art and in each of the prior art type terminations discussed above, it is important to evenly distribute tension among the load carrying components of the tension member. By ensuring that tension is equal among the load carrying components, maximum yield strength is provided. Alternately stated, a condition wherein all of the load bearing elements of the tension member maintain equal tension, the highest breaking strength is obtained since in order for the tension member to break, all of the elements must fail at the same time. Where the load bearing components of the tension member are not equally tensioned, some of the load bearing components will be overtensioned while others will be undertensioned. The result of this condition is that the total breaking strength of the rope may be reduced where the load placed upon only some of the load bearing components exceeds those components' yield strength. Possible degradation may result in such a situation. At a lower degree of tension than the tension for which the member is rated. Thus, tension members particularly in the elevator art are conventionally terminated with substantially equal loading on the load bearing components. Since most systems employing tension members are engineered for economy, any significant reduction in the maximum yield strength of the member is undesirable. Unequal loading would require that a much stronger and more costly tension member be employed in a particular system than would otherwise be required or prudent simply because of the unequal loading. Thus, it is highly desirable to create a termination that equally loads all load bearing components of a particular tension member.
In addition to creating an equally distributed load bearing arrangement it is further important to ensure that the load bearing components of the tension member do not slip in the termination either relative to each other or relative to the termination member collectively the results of both are undesirable. Load distribution in round ropes, generally steel, can be achieved by such means as compression, bonding materials and weaving. Unfortunately, the known means for effecting such terminations are not advantageously applicable for flexible flat ropes having small cross section cords and polymeric jackets. With respect specifically to prior art epoxy type terminations, a steel rope would be rosetted reselected and epoxied in a socket. Because of the diameter of the steel strands, such a method is highly effective. In flat ropes having very small diameter cords, a rosette is not sufficiently effective. Thus, the art is need of such a termination.